Date of Award

Winter 2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

First Advisor

Bryant Hollins

Abstract

This work aims to create novel applications for poly(dimethylsiloxane) (PDMS) in the field of biomicrofluidics through oxidative stress detection, doping of the polymer for intentional leaching into microdevices, and the development of low-cost implements for fabricating PDMS microfluidic devices. PDMS has become the polymer of choice for research in microfluidics due to its optical clarity, ease of fabrication, flexibility in design, good mechanical properties, and the ability to chemically modify the surface.

Biomicrofluidics enables the rapid throughput and analysis of small biological samples requiring less time investment and reagent use than traditional macroscale laboratory techniques. Polymer devices are inexpensive, easily fabricated using rapid prototyping techniques, and lend themselves well to surface chemistry modifications. A new chemical surface modification has been developed that allows the selective capture of carbonylated proteins on a PDMS microchannel.

PDMS can be doped with small molecules prior to curing of the prepolymer mixture, and these small molecules can subsequently leach into cell culture media or a microfluidic flow. By quantifying the leaching amount over time, this research lays the groundwork for tunable doped microfluidic devices that can deliver a steady low concentration dose of certain molecules into a cell culture or microdevice without human interference or risk of contamination.

PDMS soft lithography traditionally relies on cleanroom techniques such as photolithography for creation of mold masters for PDMS devices. Such methods require significant investment into specialized equipment and environments to develop molds that may not be suitable for the desired applications. This research employs computational fluid dynamics (CFD) and rapid prototyping techniques in the development of novel microfluidic designs. CFD provides verification of the flow rate and pressure drop in a microfluidic channel, ensuring that the resulting flow speeds allow the captured proteins or attached cells in culture to remain attached to the microchannel. A 3D printer and an Arduino microcontroller were used to create a spin table for coating silicon wafers in photoresist, and a UV LED light source was designed for exposing the photoresist. This approach reduces the equipment cost involved in creating microfluidic molds and allows the creation of a variety of new microfluidic devices.

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